Protector for lamp fuses



April 13, 1937. J. A. LINDER PROTECTOR FOR LAMP FUSES Filed May 27, 1936 Patented Apr. 13, 1937 UNITED STATES PATENT OFFICE morsc'roa roa Lam rmsas Application May 2'1, 1936, Serial No. 82,021

5 Claim.

This invention-relates to incandescent electric lamps or the like and relates more particularly to. lamps in which a fuse constitutes part of a lead wire.

It is the practice in certain types of incandescent electric lamps, particularly high-wattage lamps, to provide one of the lead wires with a fuse. The fuse is provided for the reason that in some cases the breaking or burning out of the filament of an incandescent electric lamp causes an arc to form therein which may result in the bursting of the bulb and the blowing of the main fuse in the main line. In some cases, the arc travels down the lead wires of the lamp and into the base and socket before the main fuse breaks,

causing considerable damage.

In practice it has been found desirable to place the lamp fuse in that portion of the lead wire extending from the bulb to the lamp base. It sometimes happens, however, that when the fuse melts the metallic vapor sets up a conductive path and an arc starts between the leads.

The present invention provides a fuse with a protective housing which serves to prevent the formation of an arc between the leads. It is necessary, however, to enclose completely the lead wire in which the fuse is incorporated and for this purpose a tubular insulative covering is provided. The tubular covering or housing is of such character as to be adjustable as to length to meet certain variations in the dimensions which vary in diflerent lamps, as will hereinafter be more fully described.

It is an object of the present invention to provide a fuse for a. lamp with a closed chamber to prevent arcing between leads by reason of the conductive path resulting from the metallic vapor formed when a fuse melts.

Another object of the invention is to provide a fus lead for a lamp with a housing capable of being adjusted to meet variations in the relative positions of the parts of the lamp.

Another object of the invention is to provide a housing of flexible material for a lamp fuse which may be varied in length to accommodate variations in the dimensions of the parts of the lamp.

The invention will be more clearly understood from the following description together with the accompanying drawing in which:

Figure 1 is a side elevational view of a lamp partly in cross section showing an embodiment of the present invention;

Fig. 2 is a view taken on line 11-11 in Fig. l; and

Fig. 3 shows a modification of the invention in which a flexible housing is used having end portions bent to vary the effective length of the housing.

The present invention may be applied to a lamp including a bulb I 0, having the usual flare tube ll sealed at ii to the bulb neck ll. The flare tube extends into the bulb and is provided with a press It through which lead wires I5 and I! extend. One end of lead wire it is connected at H to the metallic shell l8 of a base I l which base is attached to the bulb neck by cement ii. The other end of the lead wire it extends into the bulb and is connected to a support wire 22 which in turn is connected to one terminal of a filament 23.

The other terminal of the filament is connected to one end of a support wire 24, the other end of which is connected to one end of lead wire IS. The lead wire i5 extends to the center contact 25 of the base I! and is of reduced diameter to serve as a fuse 20. Surrounding the fuse is a housing or tubular casing It. This casing, in the present construction, also surrounds an exhaust tube 21 which depends from the press it.

The tubular casing preferably surrounds the fuse lead although it could be placed around the other lead and serve its purpose. To be effective, however, the tube must cover the fusible part of the lead and provide a closed chamber.

It will be understood that lamps of the character to which the present invention relates are made at a high rate of speed and certain variations occur in the dimensions of the parts and in their relative positions. For example, distance X indicated on the drawing may vary by reason of the position of the press with relation to the bulb neck or the diameter of the bulb neck may vary, thus changing the position of the base with respect to the flare tube. On the other hand, the length of the flare tube may vary.

For the purpose of providing a practical housing for the fuse lead that could be applied irrespective of variations in dimensions, a tube of flexible material is provided preferably with one or more folds or corrugations to give a diaphragm action for adjustment between the press and the lower wall 28 of the base. This lower wall is made of an insulating material such as glass and is in the form of a web which carries the contact 25 and at the same time insulates it from the shell ll.

When applying the present tubular housing, it is slipped over the lead wire and one end is thrust against the lower side of the press. If desirable, 55

' folds may be of such diameter as to frictionaily engage the wall of the flare tube so that when in position the housing will remain temporarily in position until the base Is is applied to the bulb 5 neck. The normal length of the tube 26 may great enough to bring the end of the housing in contact with the base slightly before the base is in its final position, thus forcing the tube against the press and permitting it to become adjusted and provide a closed chamber for the fuse lead.

In the modified construction shown in Fig. 3, the tube or housing 26' is cylindrical, but of flexible or soft insulative material. Thus, when the base I! is in position and the base is forced against the bulb'neck, the ends 30 and II of the housing are pressed against the web 28 and the press II and crimped over to shorten the housing to the dimension necessary. As shown, the end 3| seats in a cup or socket in the base. This construction is also shown in Fig. 1. 1

The invention contemplates any form of housing that is automatically adjusted as the base is applied and'modiflcations may be made to attain this result. For example, the housing or tube may be telescopic or one end may besoftened, and the major portion may be rigid. It has been found practical to use asbestos material for the housing although any other insulative sheet material may be employed.

By reason of the present invention, it is possible to provide a protective sleeve which effectively prevents arcing between the leads by providing a chamber for confining any metallic vapor that may form when a fuse melts, thus avoiding the formation of a destructive are.

Although a preferred embodiment of the invention is shown and described herein, it is to be understood that modifications may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

I 1. An incandescent electric lamp comprising a bulb, a flare tube sealed to the bulb neck, a base. a lead wire including a fuse extending from said flare tube to said base and a flexible insulative housing for said fuse. v

2. An incandescent electric lamp comprising a bulb, a flare tube sealed to the bulb neck, a base, a lead wire including a fuse extending from said flare tube to said base and a tubular insulative housing for said fuse, said housing having corrugations in the wall thereof whereby the effective length of said housing may be varied.

3. An incandescent electric lamp comprising a bulb, a flare tube sealed to the bulb neck, a base, a lead wire including a fuse extending from said flare tube to said base, and a tubular insuiative housing having the ends thereof in compressive relation with said flare and said base.

4. An incandescent electric lamp comprising a bulb, a flare tube having a press sealed to the neck of said bulb, a base secured to said bulb neck, lead wires extending from said press to said base, a fuse in a portion of one of said lead wires intermediate said press and base, and a flexible insulative tubular housing for said portion, said housing being compressed endwise between said base and said press to provide a closed chamber for said fuse to prevent the formation of an are between said lead wires.

5. An incandescent electric lamp comprising a bulb, a flare tube having a press sealed to the neck of said bulb, a base secured to said bulb neck, lead wires extending from said press to said base, a fuse in a portion of one of said lead wires intermediate said press and base, and a corrugated insulative tubular housing for said portion, said housing being compressed endwise between said base and said press to provide a closed chamber for said fuse to prevent the formation of an arc between said lead wires.

JOHN A. LINDER. 

